In general, the present invention is directed to a process for dyeing textile fibers, yarns and fabrics, especially cotton, cellulosic, wool, nylon and polyester products. More particularly, the present invention is directed to a process for increasing the absorptivity of textile materials in order to increase their receptiveness to dyes.
In the past, various and sundry methods and processes have been developed in order to improve the dyeability of cotton and other fibers. Further, many attempts have also been made to develop a process for dyeing fibers where the amount of dye used in the process is minimized. Decreasing the amount of dye used to dye fibers can lead to significant cost savings especially in view of the ever increasing prices of dyes and the problem of handling and disposing of spent dyebaths.
For instance, many attempts in the past to reduce the amount of dye used in a dying process for cotton fabrics or otherwise to improve the process have involved placing various chemical agents into the dye bath. Such chemical agents have included wetting agents and salts that primarily assist or facilitate exhaustion of the dyes to the fabrics. These agents also assist in leveling or uniformly applying the dye to the fabric.
Another problem that those skilled in the art have attempted to solve is the ability to dye xe2x80x9cdead cottonxe2x80x9d. Dead cotton refers to immature cotton fibers contained within cotton fabrics. Dead cotton does not readily accept dyes. Consequently, cotton containing dead cotton has sold for substantial discounts over higher quality cotton and can not be employed to manufacture fine garments.
In view of the above, various needs currently exist for methods that will improve cotton, cellulosics, wool, nylon and polyester dyeing processes. In particular, a need exists for a process for dyeing fabrics in which less amounts of dye are used during the process or deeper shades are required that are achieved by increasing dye absorption above the normal level. A need also exists for a process for dyeing cotton fabrics that contain dead cotton so that the dead cotton becomes dyed to the same extent as the other cotton fibers.
The present invention recognizes and addresses the foregoing disadvantages, and drawbacks of prior art constructions.
Accordingly, it is an object of the present invention to provide an improved process for dyeing cellulosic materials, such as cotton, wool, nylon and polyester fibers.
Another object of the present invention is to provide a process for treating materials so that they will have a greater affinity for dyes.
Still another object of the present invention is to provide a process for chemically treating cotton fibers to make the cotton fibers appear more cationic so that the fibers will be more receptive to anionic dyes.
These and other objects of the present invention are achieved by providing a process for making textile fibers more receptive to dyes. The process includes the steps of contacting the fibers with selected amine oxides. It is believed that the amine oxide reacts with cellulosic fibers, making the fibers appear as if they are more cationic. Once contacted with an amine oxide, the cellulosic fibers are heated to a specific temperature for optimum yield and at least partially dried. The said fibers are then dyed with an anionic dye. It has been discovered that by treating the said fibers with an amine oxide makes the fiber absorb anionic dyes quicker, and dye to a deeper shade versus the untreated fiber.
Materials that can be treated in accordance with the present invention include cotton, and other cellulosic materials. Wool, nylon and polyester also respond positively albeit by what we think is an alternative mechanism such as the amine oxide functions like a carrier plasticising and swelling the fibers. The materials treated can be fibers, yarns, or fabrics. The amine oxides used in the process of the present invention can vary. For most applications, the amine oxides can be represented by the following formula: 
wherein
R1, R2 and R3 are C1 to C8 linear or branched alkane radicals or hydroxyalkyl groups.
R1 and R2 can be linked to form five and six membered heterocyclic rings.
R1, R2 and R3 can be the same or different.
Examples of amine oxides includes: N-methylmorpholine oxide, N-(2-hydroxyethyl)morpholine oxide, N,N-dimethylethanolamine oxide, N-ethylmorpholine oxide, N,N-dimethyloctylamine oxide, and mixtures thereof. In one embodiment of the present invention, the amine oxide can be a trialkylamine oxide, such as trimethylamine oxide. Most amine oxides besides making cellulosic fibers more cationic have a tendency to dissolve the fibers causing the fibers to bond together, creating a stiffer product. It has been discovered, however, that trimethylamine oxide does not cause the cellulosic fibers to dissolve resulting in an even softer hand than the untreated fiber.
In order to apply the amine oxide to the textile material, the material can be dipped into an aqueous solution or dispersion containing the amine oxide. For instance, the aqueous solution can contain an amine oxide in an amount from about 20% to about 50% by weight. The aqueous mixture can be applied to the textile material so that the add on causes the weight of the material to increase up to 120%, and particularly from about 50% to about 120%.
In an alternative embodiment of the present invention, an amine oxide composition can also be printed onto the textile material. For instance, the amine oxide can be combined with a thickener for forming a printing paste. The printing paste is applied to a fabric containing textile fibers according to a particular design. Once the fabric is dyed, the design will then appear on the fabric as a more deeply dyed area.
Once the amine oxide is applied to the textile material, the textile material is then heated, such as to a temperature of from about 140xc2x0 F. to about 300xc2x0 F., and particularly from about 200xc2x0 F. to about 250xc2x0 F. After being heated, if desired, the textile materials can then be rinsed.
In order to dye the textile materials after treatment with the amine oxide, the materials can be dipped into a dye bath containing an anionic dye. In general, any suitable anionic dye may be used. In one embodiment, the dye bath can contain a salting agent, such a metal salt, that facilitates exhaustion of the dye to the textile material. Such salting agents have been used in the past. However, it has been discovered by the present inventors that less salting agent is required to achieve the required shade if the textile materials have been previously contacted with an amine oxide. For instance, a salting agent can be present in the bath at a concentration of less than about 120 grams/liter, and particularly from about 5 grams/liter to about 120 grams/liter.
Other objects, features and aspects of the present invention are discussed in greater detail below.
The present invention is generally directed to a process for treating textile fibers namely cotton, cellulosics, wool, nylon and polyester fibers, in order to make them more receptive to dyes. More particularly, it is believed in the case of cotton and cellulosics, the process of the present invention increases the cationic charge of the cellulosic materials making them have a greater affinity for anionic dyes. In this manner, less dye and salt is required when dyeing the materials. The process of the present invention generally includes the step of contacting the cellulosic materials with an amine oxide. The amine oxide we believe chemically reacts with the cellulosic material causing the cellulosic material to have an increased cationic charge.
In the past, amine oxides have been used in order to dissolve cellulose from wood and other sources and then form cotton-like fibers from the dope after extrusion into water, which is a solvent for the amine oxide but not for the cellulose.
As opposed to the above prior art, in one embodiment, the present invention is directed to treating cotton fibers with amine oxides without substantially dissolving the fibers. It is believed the mechanism in the case of cotton is that the amine oxide increases the cationic charge of the fibers increasing their affinity for anionic dyes. Besides minimizing the amount of dye used to dye cotton fibers and other cellulosic materials, the process of the present invention offers many other advantages and benefits.
For instance, the present inventors have discovered that dead cotton contained within fabrics will react with the amine oxide making the dead cotton capable of receiving dyes. In the past, fabrics made with dead cotton were considered inferior in that the dead cotton would not dye to the same extent as the other cotton fibers and would leave light spots on the resulting fabric. The process of the present invention, however, can be used to overcome the disadvantages associated with fabrics containing dead cotton.
In certain circumstances, the process of the present invention can also remove pilling on fabrics containing cotton fibers. For example, the amine oxide can be used to plasticize the fine fibrils that cause pilling. The treated fibrils will then weld to other fibers contained in the fabric.
Because it has been discovered that some amine oxides plasticize cellulosic materials while others will not, the process of the present invention can also be engineered to create a fabric having particular desired hand characteristics. Specifically the hand characteristics of a fabric can be controlled by selecting particular amine oxides for use in the process and by controlling the concentration of the amine oxides in the solution that is contacted with the fabric.
Various other advantages and benefits of the present invention will be made apparent from the following description.
The following is one embodiment of a process according to the present invention for treating cellulosic materials for increasing their affinity to dyes. The following description will be primarily directed to fabrics containing cotton fibers. It should be understood, however, that the process of the present invention is also applicable to treating fibers themselves, to yarns made from the fibers, or to other textile materials, such as wool, nylon and polyester or mixtures of said fibers. The mechanism in the case of the other fiber types is believed to be based on the xe2x80x9csuper solventxe2x80x9d characteristics of the amine oxide water combination causing the fibers so treated to be less crystalline and more amorphous. Further, although the following description will discuss treating cotton fibers, the process of the present invention can also be used to treat other cellulosic materials such as wool.
As described above, in general, the process of the present invention is directed to treating cotton, cellulosics, wool, nylon and polyester fibers contained in fabrics with one or more amine oxides. The fabric treated in accordance with the present invention can also be a blend of fibers. For instance, it is believed that the process can be used advantageously to dye fabrics containing a mixture of cotton and polyester fibers.
Various amine oxides can be used in accordance with the present invention for treating textiles. For instance, amine oxides that dissolve or plasticize cellulosic materials and amine oxides that do not dissolve or plasticize cellulosic materials can both be used. In one embodiment, an amine oxide can be used that has the following formula: 
where
R1, R2 and R3 are C1 to C8 linear or branched alkane radicals or hydroxyalkyl groups.
R1 and R2 can be linked to form five and six membered heterocyclic rings.
R1, R2 and R3 can be the same or different.
Particular examples of amine oxides that dissolve cellulosic materials include N-methylmorpholine oxide, and N,N-dimethylethanolamine oxide.
The present inventors discovered various amine oxides that do not dissolve cellulosic materials. To the inventors"" knowledge, all amine oxides used in the past to treat cellulosic textiles dissolved and plasticised the materials. Amine oxides, however, that generally do not dissolve cellulosics include trialkylamine oxides, such as trimethylamine oxide. The use of amine oxides that do not dissolve cellulosic materials offer various benefits and advantages in certain applications. For instance, if the amine oxide were to dissolve or plasticize the cotton fibers, the resulting fabric would become stiffer. Using amine oxides that do not dissolve or plasticize the cotton fibers results in fabrics having a softer hand.
In order to apply the amine oxide to the textile materials, various methods and processes can be used. For instance, the amine oxide can be sprayed or printed onto a fabric. In an alternative embodiment, the fabric can be dipped into an aqueous solution containing an amine oxide.
For instance, in this embodiment, one or more amine oxides can be combined with water. The amine oxides can be present in the aqueous solution in an amount from about 20% to about 50% by weight. The amine oxide can be added to the aqueous solution as a preformed composition or can be added to the solution as separate reactants that later form an amine oxide. For instance, a tertiary amine and hydrogen peroxide can be added to the solution which will then form the amine oxide.
Although not necessary, the aqueous solution containing the amine oxide can contain other ingredients if desired. For instance, the aqueous solution can contain surfactants, wetting agents, thickening agents and/or deaerating agents. The solution can be pH adjusted with common acids and bases.
Once the aqueous solution is formed containing the amine oxide, a fabric containing cotton fibers is dipped into the solution and the solution is padded onto the fabric. The temperature of the solution will vary depending upon the ingredients contained within that solution. For most applications, however, the solution need only be at room temperature.
The add on rate to the fabric will also vary depending upon the particular application. Such factors to consider are the concentration of the amine oxide in the aqueous solution, how much stiffening of the fabric is desired if the solution contains an amine oxide that plasticizes cellulosic materials, the shade of dye that is to be used, plus various other factors. For most applications, however, the add on rate will be such that the fabric increases in weight after being dipped into the solution in an amount from about 50% to about 120%, and particularly from about 50% to about 75%.
Once the amine oxide is applied to the fabric, the fabric is heated in order to substantially dry the fabric and to ensure the amine oxide has plasticized or reacted with the cotton fibers. To ensure uniformity of the treatment throughout the fabric, the fabric should be substantially dry. During the drying cycle, the fabric will reach the optimum amine oxide content (typically 9-12%) for optimum performance. For instance, the fabric can be heated to a temperature of from about 1400 F. to about 300xc2x0 F., and particularly from about 200xc2x0 F. to about 250xc2x0 F. In general, lower temperatures require longer drying times. In one embodiment, the treated fabric is concentrated by being contacted with steam. We believe that there is an optimum high concentration of amine oxide in water that is the most effective concentration with some water being important for efficient use of the amine oxide.
After being heated, the fabric can then be rinsed with water in order to remove any unreacted materials. In general, the fabric can simply be rinsed with water or with water containing a surfactant or soap.
After being rinsed, the fabric is then ready to be dyed. For most applications, in order to dye the cotton fabric, the fabric will be immersed in a dye bath containing one or more anionic dyes. In general, any suitable dye may be used in the present invention including sulfur dyes, direct dyes, fiber reactive dyes, vat dyes (indigo), and the like.
Besides containing one or more dyes, the cotton dye bath can contain various other ingredients. For instance, in one embodiment, the dye bath will contain a salting agent that facilitates application of the dye to the fabric. Specifically, the salting agent when present in the dye bath shields the cotton negative charge and makes the dye less soluble so that the dye can be absorbed onto the fabric. Salting agents that may be used according to the present invention include various metal salts, such as sodium salts. Particular salting agents include sodium chloride or sodium sulfate.
These salting agents have been used in the past in dyeing processes. It has been discovered by the present inventors, however, that smaller amounts of salting agents are needed when cotton fabrics have been treated with an amine oxide in accordance with the present invention. Specifically, better results are obtained with 30 to 50 percent less salting agents. In this regard, the salting agents can be present in the dye bath at a concentration of up to about 120 grams/liter, and particularly at a concentration of less 100 grams/liter. More particularly, the salting agents can be present within a dye bath in an amount from about 5 grams/liter to about 100 grams/liter. Such a reduction in salt results in a significant and beneficial reduction in dye-bath wastes.
Besides salting agents, various other ingredients can also be present in the dye bath. Such other ingredients include lubricants, softeners, wetting agents, pH adjusters, and buffers.
In an alternative embodiment of the present invention, instead of applying the amine oxide to the fabric by dipping the fabric into a solution, a composition containing the amine oxide can be printed onto the fabric. In this embodiment, the amine oxide can be combined with a thickener to form a print paste. Thickeners that can be used, for instance, include gums or well known acrylic thickeners like the cross-linked polyacrylic acid types.
Once the print paste is formed, the paste can then be printed onto the fabric using, for instance, a gravure printing device. The amine oxide composition can be applied uniformly to a surface of a fabric or can be applied to the fabric according to a predetermined pattern. If applied according to a predetermined pattern, once the fabric is dyed, the pattern will become visible. Specifically, the areas of the fabric treated with the amine oxide composition will have a darker shade than the remainder of the fabric. Through this process, various unique and aesthetic fabrics and dye patterns can be formed.
In still another alternative embodiment of the present invention, an amine oxide composition can be used to emboss a design into a fabric containing cellulosic fibers. In this embodiment, the fabric is treated as described above with an amine oxide that readily plasticizes cotton such as NMMO or DMHEAO. Once treated, a heated stamp is pressed into the fabric according to a desired design. The temperature and pressure of the stamp will cause cellulosic fibers contained in the fabric to plasticize and bond together. The area of the fabric contacted with the stamp thus becomes stiffer than the remainder of the fabric. In this manner, a design can be embossed into the fabric much like a watermark on a paper product. Further, once the fabric is dyed, the embossed pattern will have a darker shade.
As described above, besides cellulosic materials, the process of the present invention can also be used to facilitate dying other textile materials, such as wool, nylon and polyester. In this embodiment, it is believed that the amine oxide acts as a solvent and is absorbed into the textile material. In this manner, the textile material has a greater affinity for dyes. Thus, when dying textile materials such as wool, nylon and polyester, the amine oxide chosen for the process is preferably an amine oxide that has solvent-like qualities. For instance, preferably an amine oxide is used having a relatively low molecular weight.
The present invention may be better understood with reference to the following examples.